3 ms·

The fossils in the La Brea tar pits in Los Angeles http://www.skepticblog.org/2013/03/27/mysteries-of-the-tar-pits/ http://www.skepticblog.org/2013/03/27/myste

The fossils in the La Brea tar pits in Los Angeles http://www.skepticblog.org/2013/03/27/mysteries-of-the-tar-pits/ http://www.skepticblog.org/2013/03/27/mysteries-of-the-tar-p... provide a rich record of a variety of mammal and bird species going through almost 30,000 years of the last glacial-interglacial cycle. What's remarkable about the fossils is the statis in the body forms of the wide variety of animals trapped in the tar pits. Significant climate change resulted in indistinguishable evolutionary change in those animals. As scientists continue to work on predicting the probable effects of future climate changes, looking back on verifiable examples like well dated fossil beds will be helpful in putting bounds on the predictions.

btilly 14y ago
There is nothing remarkable about that. 30,000 years is very short evolutionarily. The best response to climate change in that time frame is migration, not adaptation.
- Daniel_Newby 14y ago
  30,000 is an evolutionary eternity. The huge variety of bizarre dog breeds was created over a few centuries. Foxes were turned from nigh untameable wild animals into pets in a few decades.
  - jessriedel 14y ago
    That's not evolution, that's selective breeding by humans.
    - agildehaus 14y ago
      Selection is a component of evolution. Human selection is just one type of it, natural being the other. Wolves did evolve into dogs, but not naturally by our definition of "natural".
  - btilly 14y ago
    Yes, 10,000 years is a long enough time to create a whole new species under normal circumstances. Under the forced breeding that people do, it goes even faster. But normally a species is pretty well adapted to its environment and does not have trivially obvious improvements to make, and therefore changes slowly. Therefore the the average mammalian species manages to survive mostly unchanged for about a million years or so (figure shamelessly stolen from http://en.wikipedia.org/wiki/Background_extinction_rate http://en.wikipedia.org/wiki/Background_extinction_rate - and they cite a 1993 study for it). Thus one would expect, on average, that 97% of the mammalian species that were around 30,000 years ago that to still be around and recognizably be the same kind of animal. This is not actually so, and the main reasons are extinction events caused by people, and the effects of domestic breeding on chickens, dogs, carrots, tomatoes, and so on. But outside of types of things created by humans, there aren't a whole lot of new species running around that didn't exist in pretty close to their current form 30,000 years ago. For example there is likely less genetic difference between you and our ancestors 30,000 years ago than there is between you and an Australian aborigine.
  - lobster_johnson 14y ago
    It's not an "eternity" by any means, but it's enough for selection to take place. Humans are thought to have developed lactose tolerance within the last 10k years, for example (probably closer to 6k, if I remember correctly). In other observed cases, significant selection occured in just a few decades [1]. [1] http://news.nationalgeographic.com/news/2006/07/060714-evolution.html http://news.nationalgeographic.com/news/2006/07/060714-evolu...

btilly 14y ago

There is nothing remarkable about that. 30,000 years is very short evolutionarily. The best response to climate change in that time frame is migration, not adaptation.

Daniel_Newby 14y ago
30,000 is an evolutionary eternity. The huge variety of bizarre dog breeds was created over a few centuries. Foxes were turned from nigh untameable wild animals into pets in a few decades.
- jessriedel 14y ago
  That's not evolution, that's selective breeding by humans.
  - agildehaus 14y ago
    Selection is a component of evolution. Human selection is just one type of it, natural being the other. Wolves did evolve into dogs, but not naturally by our definition of "natural".
- btilly 14y ago
  Yes, 10,000 years is a long enough time to create a whole new species under normal circumstances. Under the forced breeding that people do, it goes even faster. But normally a species is pretty well adapted to its environment and does not have trivially obvious improvements to make, and therefore changes slowly. Therefore the the average mammalian species manages to survive mostly unchanged for about a million years or so (figure shamelessly stolen from http://en.wikipedia.org/wiki/Background_extinction_rate http://en.wikipedia.org/wiki/Background_extinction_rate - and they cite a 1993 study for it). Thus one would expect, on average, that 97% of the mammalian species that were around 30,000 years ago that to still be around and recognizably be the same kind of animal. This is not actually so, and the main reasons are extinction events caused by people, and the effects of domestic breeding on chickens, dogs, carrots, tomatoes, and so on. But outside of types of things created by humans, there aren't a whole lot of new species running around that didn't exist in pretty close to their current form 30,000 years ago. For example there is likely less genetic difference between you and our ancestors 30,000 years ago than there is between you and an Australian aborigine.
- lobster_johnson 14y ago
  It's not an "eternity" by any means, but it's enough for selection to take place. Humans are thought to have developed lactose tolerance within the last 10k years, for example (probably closer to 6k, if I remember correctly). In other observed cases, significant selection occured in just a few decades [1]. [1] http://news.nationalgeographic.com/news/2006/07/060714-evolution.html http://news.nationalgeographic.com/news/2006/07/060714-evolu...